RR-WRF system update

RR-WRF system was updated: the 03, 09, 15 and 21 UTC model runs have been removed.

The updated version is the same, but with only 4 runs/day (00, 06, 12 and 18 UTC).

This measure was taken because there was no noticeable differences and improvements for the secondary runs (03, 09, 15 and 21 UTC) in relation to the main runs (00, 06, 12 and 18 UTC). Because we now have more computing time available, a number of operational-experimental instances will be added soon.

Best regards, RRWRF team.